President Bush “convinces himself to believe what suits his needs at the moment,” and has engaged in “self-deception” to justify his political ends, Scott McClellan, the former White House press secretary, writes in a critical new memoir about his years in the West Wing.

In addition, Mr. McClellan writes, the decision to invade Iraq was a “serious strategic blunder,” and yet, in his view, it was not the biggest mistake the Bush White House made. That, he says, was “a decision to turn away from candor and honesty when those qualities were most needed.”